1. Technical Field
The present invention relates to a plating method, more particularly to a plating method for a radio frequency (RF) device and to a radio frequency device produced by this method.
2. Description of the Related Art
As a result of developments in mobile communication, optical communication, and satellite communication, as well as the popularization of mobile communication terminals, various types of RF devices for processing RF signals, such as filters, duplexers, waveguides, etc., are being mass-produced.
When processing high-frequency RF signals, such as microwaves, there may be an occurrence of the “skin effect,” which describes the phenomenon of the high-frequency current becoming maximum at the surface. In order to obtain the desired properties in a desired frequency range, an RF device for processing high-frequency RF signals must be capable of reducing alternating current loss. For this purpose, a plating process of plating an interior of the RF device may be selected, where silver plating is generally performed.
Typically, the factors affecting alternating current loss in a high-frequency RF device are known to be the surface roughness of the internal surfaces of the waveguide and the plating method. Thus, to reduce loss, there is a need to use a plating method that is appropriate for a product having a complicated shape, as well as to select a suitable plating liquid.
By using a suitable plating treatment, it is necessary to provide uniform deposition properties and good skin smoothness, lower electrical resistance, and increase adhesion strength to the substrate layer.
The thickness of the plating layer is also closely related to a physical property, i.e. the skin effect in high-frequency ranges. The skin depth according to the skin effect can be expressed by Equation 1.
                    1                              π            ⁢                                                  ⁢            f            ⁢                                                  ⁢            μσ                                              [                  Equation          ⁢                                          ⁢          1                ]            
In Equation 1 above, π is a constant, μ is magnetic permeability, f is frequency, and σ is electrical conductivity.
The RF devices to which a silver plating treatment is applied are usually first shaped from aluminum or an aluminum alloy and afterwards are subject to the silver plating treatment. In general, an RF device was produced by fabricating its shape from aluminum or an aluminum alloy using casts, etc., and then immersing the shape in a plating liquid.
While this method of silver-plating an RF device may be advantageous in terms of loss and appearance quality, the method may incur high costs and thus may not provide an economical advantage.
In recent times, there have been attempts to use copper plating as a substitute for the expensive silver plating, but copper plating may not provide desirable properties in terms of appearance quality, in relation to aesthetics and oxidation.